Fuel injector for internalcombustion engines



G. W. ,A. GREEN Filed Sept. 24, 1943 FUEL INJECTOR FOR INTERNAL-COMBUSTION ENGINES March 5, 1946.-

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Aitorr'zey PatentedMarLS, 19,46

FUEL INJECTOR FOR INTERNAL- COMBUSTION ENGINES George Wilfrid Acland Green, Staines, England,

assignor to Lagonda Limited, Staines, Middles'ex, England Application September 24,1943,- Serial No. 503,708

In Great Britain September 25, 1942 1 Claim (cl. 137-153) This invention relates to'that type of fuel injector, for internal combustion engines, in which a spring-loaded needle valve movable axially of the injector body is adapted to be displaced periodically from its seat, afforded in a nozzle member situated at one end of the injector body, by fuel supplied under pressure to the interior of the injector in order to open a jet orifice or orifices through which fuel under pressureis then discharged.

very high degree of concentricity between the seating faces on the needle valve and nozzle member respectively and the guiding surfaces of the needle valve and its guide without which correct functioning of the nozzle is impossible since fuel leakage past the valve seat will occur or the needle valve may even be deformed and jammed.

The present invention provides in a fuel injector of the type stated in the first paragraph above, the combination of a guide sleeve for the needle valve stem, said sleeve having diametral clearance in the injector body so as to be selfcentering in the course of assembling the injector components, and means for rigidly retaining the sleeve in alignment with the valve 'seat on completion of assembly and throughout the operational movements of thevalve.

With this arrangement the guide sleeve will be brought into exact alignment with the valve seat in the nozzle member to achieve the previously known effectof the valve being free to move to and from the seat without restraint from undesirable transverse forces, but in a manner which avoids thedisadvantages of a freely fioating guide, namely that disturbing influences may cause deviation of the needle valve when open and the consequent danger of the valve not again descending centrally to its seat without first striking the seat asymmetrically and then sliding to the fully closed position-an action which would cause uneven wear of the valve seat and imperfect sealing.

By way of non-limitative example two constructional forms of fuel injector embodyingthe invention are illustrated, in the accompanying drawing'in which Figure 1 is a longitudinal sectional view of one form of fuel injector embodied in my invention; Fig. 2 is a fragmentary vertical sectional view of a modified view of fuel injector embodied in my invention and Fig. 3 is a transverse sectional view taken on line 3-3 of Fig. 1.

Referring first more-particularly to Fig. 1, the fuel injector body I is bored longitudinally from -l A manufacturing difiiculty inseparable from such an injector is the necessity of attaining a I end to end, with a stepped-down portion 2 near its inner or lower end. The nozzle member 3 is a close diametral fit in this reduced bore and has a locating flange l which rests on the step, and

through which radial fuel ports 5 are drilled. The needle valve 6 is axially slidable within the nozzle member 3 to control delivery of fuel to the jet orificeis) formed in the outer end of the said member'past a valve seat 1 within the nozzle member in the usual manner. This valve 6 has a shoulder 8 and, beyond the shoulder, a stem 9 which is aclose sliding fit in a guide sleeve l0 disposed within the bore of the injector body I. The guide sleeve III is given diametral clearance in the said bore as is clearly shown on the drawing.

A tubular distance piece ll within the bore of the injector'body i bears on the upper face of the guide sleeve l0 .and is retained by the inner spigot portion I2 of a spring housing'member i3, one end of which is screw-threaded into the upper or outer endof the injector body I. The distance piece, which is a reasonably good fit in the bore of the injector body (although accuracy of this fit is not obligatory) has longitudinal grooves M in its outer periphery (four in the illustrated example) for the passage of fuel to the nozzle member 3 via the radial fuel ports 5 as shown more clearly in Fig. 3. Within the tubular distance piece II is a virtual extension iii of the needle valve stem 9; it has a tapered lower portion It centering in an axial opening il in the upper end of the valve stem, and it carries, at its'upper end, a seating washer l8 fonthe valve loading spring I9. The last mentioned is accommodated in the aforesaid housing member 13 and its other end engages another seating washer 20 which is guided by a plug 2| screwed into the cap 13a of the spring housing member i3.

On assembling the described components of the fuel injector the needle valve 6 is located in the nozzle member 3. The guide sleeve In for'the valve stem 9 in its turn is located by the valve stem and as the spring housing I3 is screwed home, applying pressure to the loading spring IS, the point of the needle valve; 9 is pressed by the pressure of spring l9 into the seating in the nozble 3 and the guide sleeve Ill is gradually brought into line by the needle valve stem 9 and by the reactions at the faces of the nozzle member 3 and-the distance piece ll until-it is finally clamped securely in true alignment with the valve seat I in the nozzle member as required to enable the valve to rise from and fall to its seat without restraint'from undesirable transverse forces.

.so that the needle valve cannot possibly deviate from its true axial position with the result that, in closing, there is no danger of it striking the valve seat oil-centre, as could happen with a floating guide, and then sliding to the fully closed position, i; e., there is no danger of uneven wear of the valve seat and resultant leakage at the place of wear.

In the form illustrated by Fig. 2 the upper part Illa of the guide sleeve In for the needle valve stem 9 is externally stepped down to .present a shoulder 22 and the lower part lid of the hollow distance piece I5 is internally enlarged to pass over the reduced portion Ilia of the guide sleeve and to bear on the shoulder 22 while standing clear of the top of the guide sleeve. The guide sleeve I has diametralclearance in the bore of the injector body while diametral clearance is also afforded between the upper part Illa of the sleeve and the lower part I511 of the distance piece I! so that, as before, the sleeve is free to align itself. In this arrangement the clamping force is applied to the guide sleeve at a locus below the top of the sleeve, namely, at the shoulder 22 presented by the reduced portion, the self-aligning action being thereby assisted in certain circumstances.

I claim:

In a fuel injecting valve for internal combustion engines, an injector body, a spring loaded needle valve spindle movable axially of the iniector body, a valve seat member situated at one end of the injector body h; ,ving an annular seat, a guide sleeve for the needle valve in said injector body, said guide sleeve having diametral clearance in the injector bodyso that said needle valve spindle may be accurately aligned with the valve seat during assembly of the injector components, and means for rigidly retaining the sleeve in that position in which the valve seat is aligned with said needle valve on compietiom-of assembly thereof and throughout the operational movement of the valve.

GEORGE WILFRID ACLAND GREEN. 

